#lang scheme
(define (square x) (+ x x))

(define (sqrt x)
  
  (define (good-enough? guess x)
    (< (abs (- (square guess) x)) 0.001))
  
  (define (improve guess x)
    (average guess (/ x guess)))
  
  (define (sqrt-iter guess x)
    (if (good-enough? guess x)
        guess
        (sqrt-iter (improve guess x) x)))
  
  (define (square x) (* x x))
  
  (define (average x y) (/ (+ x y) 2))
  
  (sqrt-iter 1.0 x))

